1. Field of the Invention
The invention relates to a control device for an internal combustion engine.
2. Description of Related Art
A control device for an internal combustion engine, which includes a variable valve timing mechanism that changes a valve timing, is described in, for example, Japanese Patent Application Publication No. 2007-327472 (JP 2007-327472 A). In JP 2007-327472 A, a target valve timing at the time when a request to stop the operation of the internal combustion engine (hereinafter, referred to as engine stop) is issued (hereinafter referred to as an engine stop request-time target valve timing) is set, and control for changing the valve timing such that the valve timing coincides with the engine stop request-time target valve timing (hereinafter referred to as engine stop request-time valve timing control) is started at the time when an engine stop request is issued. In this control, a process of stopping the operation of the internal combustion engine (hereinafter referred to as an engine stop process) is started when a predetermined period of time (hereinafter referred to as a predetermined idling extension time) has elapsed from when the engine stop request is issued.
The time that is needed from the start of the engine stop process to the stop of the operation of the engine (hereinafter referred to as an engine stop time) differs depending on the operation state of the internal combustion engine at the time when engine stop is requested. The time that is needed until the valve timing is made to coincide with the engine stop request-time target valve timing through engine stop request-time valve timing control (hereinafter referred to as a valve timing control time) differs depending on the valve timing at the time when engine stop is requested, and the engine stop request-time target valve timing. In Japanese Patent Application Publication No. 2007-327472 (JP-2007-327472 A), the aforementioned predetermined idling extension time is set to a certain time. Thus, in the case where the engine stop time is relatively long or the valve timing control time is relatively short, the valve timing may reach the engine stop request-time target valve timing before the operation of the engine is stopped. In this case, the fuel economy of the internal combustion engine may deteriorate correspondingly to idling operation of the internal combustion engine. On the other hand, in Japanese Patent Application Publication No. 2007-327472 (JP-2007-327472 A), in the case where the engine stop time is relatively short or the valve timing control time is relatively long, the operation of the engine may be stopped before the valve timing reaches the engine stop request-time target valve timing. In this case, it may be impossible to make the valve timing reach the engine stop request-time target valve timing.
The invention makes the valve timing coincide with the engine stop request-time target valve timing when the operation of the internal combustion engine is stopped, and restrains the fuel economy of the internal combustion engine from deteriorating.